Process of carburizing iron and steel



Patented Mar. 19, 1929.

UNITED STA OFFICE.

I ROBERT G. GUTHRIE AND OSCAR J, WOZASEK, CHICAGO, ILLINOIS, ASSIGNORS TO PEOPLES GAS IBY-PRODUCTS CORPORATION,

TION OF ILLINOIS.

OF CHICAGO, ILLINOIS, A CORPORA- PROCESS OF CABB'URIZING IRGN' AND STEEL No Drawing.

The invention relates to new and useful improvements in a process of carburizing iron or steel by a gaseous treatment. (The present application is a continuation in part of our prior application Serial No. 220,632, filed September 19, 1927.)

- An object of the invention is to produce a carburized steel of given depth of case in less time than has been required by former processes.

A further object of the invention isto provide a process wherein the carburizing efficiency of a carbonaceous gas is increased.

A still further object of the invention is to provide a process wherein the carbon concentration of the case is increased for a given depth of penetration.

A still further object of the invention is to provide a process wherein the acceptability of the iron or steel is increased for a given carbonaceous gas.-

These and other objects 'will in part be obvious and will in part be hereinafter more fully disclosed.

The invention in its broadest aspect relates to a process of carburizing iron or steel which consists in heatingthe iron or steel to an elevated temperature in a container or retort and subjecting said iron or steel while maintained at the elevated temperature to a carbonaceous matter, preferably a carbonaceous gas. The carbonaceous gas may he of any well lznown character, but to get the best efficiency must be a practically dry or dehydrated carburizing gas. it is found in practice that city gas being: the illuminating gas delivered through mains in cities, is excellently adapted for the purpose. This gas is often referred to as town gas.

The process also includes the introduction into the retort while at an elevated tempcrasure of a minute quantity of onyg'en, either roe or combined. The oxygen is introduced either immediately before or slmultaneously ,with the initial introduction of the carboua ceous gas. lt-is essential that the oxygen shall be introduced at this beginning of the *h the carbonaceous so as to catalyst, which. greatly in "midity of penetration of the ron or steel during the subof the catnient w steel to the action iron v this Serial No. 329,942.

rapidity of the penetration the period of time necessary to obtain a given depth of case with afigiven gas is materially decreased.

When certain reluctant steels and irons, such as the so-called abnormal steels and irons? are to be treated, sulphur, either free or combined. is added in minute quantities to the retort. lVhen sulphur is added, a greater concentration of carbon for a given depth of case is obtained in a given time. The addition of the sulphur increases the acceptability for carbon of the so-called abnormal iron or steel. Sulphur may be added to the retort at the beginning of the treatment with the carbonaceous gas. Excellent results have been. obtained, however, by add ing the sulphur in minute quantities at other times during the carburizing process and continuously throughout the carburizing' brought to a temperature between 1500 and 1,800 degrees 1?. When the temperature reached approximately 1750 degrees F., the town gas was allowed to enterv the bottom of the retort and coincidental with the introduction of the gas, ten drops of water permitted for a total of three minutes was allowed to drip into the infiowino; This supplied the oxygen to form the oxide catalyst. In the carrying out of this process. the carbonaceous gas was supplied continuously throughout the run and for the first three minutes only of the run. oxygen was added in the manner stated. after which the supply of the water was cut off and the supply of the carbonaceous gas continued. The carbonaceous as passed over the iron an d steel parts and out of an exit at the top where it was burned to prevent contamination of the atmosphere.

lit found by this process that the rapldity .netratiou of the carbon into the .cl during the carburizingr of the i ORiIlC'E to obtain iis was accomwill also be understood that the oxygen'may be supplied to the retort in other forms. lit is essential, however, in connection with the oxygen that a very minutequantity shall be introduced into the retort at the beginning of the run,and in connection with the sulphur, a minute quantity is introduced into the retort either at the beginning of the run or at any time during the treatment of the iron and steel with the carbonaceous gas. With the use of sulphur it is possible to carburize and at the same time reduce or minimize the abnormality of an abnormal iron or steel in the presenceof a carbonaceous gas of normally low carburizlng efliciency. In other words,by

this process the oxygen iron catalyst increases the efliciency of the inherent efficient carbonaceous gas and the sulphur increases the acceptability for carbon of the so-called abnormal iron or steel.

It will bejl nderstood that the, invention may be carried out in other ways without departing flour-the spirit thereof as set forth in the appended claims.

Having fully described our invention, what we claim as new and desire to secure by Letters Patent, is

1. The process of carburizing iron or steel comprising heating the iron or steel to an 'elevated temperature in a container or retort,

gas and treating said iron or steel at the beginning of the treatment with the carbonaceous gas with a minute quantity of oxygen to form an oxide catalyst whereby the rapidity of penetration of the carbon into the iron or steel during the carburizing of the same is greatly increased.

2. The process of carburizing iron or steel comprising heating the iron or steel to an elevated tel'uperature in a container or retort, subjecting said iron or steel While maintained at the elevated temperature to a dehydrated carbonaceous gas and treating said iron or steel at the beginning of the treatment with the carbonaceous gas with a minute quantity of oxygen to form an oxide catalyst whereby the rapidity of penetration of the carbon into the iron or steel during the carburizing of the same is greatly increased.

3. The process of carburizing iron or steel comprising heating the iron or steel to an elevated temperature iii a container or retort,

subjecting said iron or steel while maintained at the elevated temperature to a carbonaceous gas, treating said iron or steel at the beginning of the treatment with the carbonaceous gas with a minute quantity of oxygen to form an oxide catalyst and with a minute quantity of sulphur during the treatment with the carbonaceous gas whereby the efiiciency of the carbonaceous gas is increased and the acceptability of the iron or steel for carbon is increased.

In testimony whereof, we aflix our signatures.

ROBERT e. GUTHRIE. OSCAR .rwozxsnx. 

